Regulate the chemical property of the carbon nanospheres layer modified on the surface of sodium metal anode to achieve high-load battery

The energy density of batteries can be increased by using high-load cathode material matched with sodium (Na) metal anode. However, the large polarization of the battery under such harsh conditions will promote the growth of Na dendrites and side reactions. Carbon materials are regarded as ideal modify layers on Na metal anode to regulate the Na⁺ plating/stripping behavior and inhibit the Na dendrites and side reactions due to their light weight, high stability and structural adjustability. However, commonly used carbon nanotubes and carbon nanofibers cannot enable these modified Na metal anodes to operate stably in full batteries with a high-load cathode (> 15 mg·cm⁻²). The most fundamental reason is that abundant polar functional groups on the surface bring serious side reactions and agglomerations lead to uneven Na⁺ flow. Here, a proof-of-concept study lies on fabrications of carbon nanospheres with small amount of polar functional groups and sodiophobic components on the surface of Na metal anode, which significantly enhances the uniformity of the Na⁺ plating/stripping. The assembled symmetric battery can cycle stability for 1300 h at 3 mA·cm⁻²/3 mAh·cm⁻². The full battery with high-load Na₃V₂(PO₄)₃ (30 mg·cm⁻²) maintains a Coulombic efficiency of 99.7% after 100 cycles.